TiN/TiO₂ composite coatings: preparation, microstructures and tribological properties

In our present work, TiN suspension was sprayed onto the 316 stainless steel substrate using the suspension high velocity oxy fuel thermal spray. An in-situ reaction between TiN and O₂ occurred during the spray process to form TiO₂ and TiN/TiO₂ composite coatings were fabricated. The phase evolution, microstructures and tribological properties of TiN/TiO₂ composite coatings were studied. Results showed that the interface between the coating and the substrate was well bonded, which was mainly owing to the in-situ reaction heat and the sufficient deformation of particles. The structure of molten particles, small grain size and low porosity could contribute to improving the mechanical and tribological properties of the in-situ coating. A schematic exfoliation process of TiN/TiO₂ composite coating was proposed to analyze the failure of coatings. The antiwear mechanisms of the TiN/TiO₂ composite coatings were discussed. The good cohesive bonding strength and high hardness of the TiN/TiO₂ composite coating, the pinning role of TiN in crack propagation, and the newly formed TiO₂ in the friction layer during the sliding test contributed to the improvement of tribological properties for the TiN/TiO₂ composite coating. This work could provide a reference for the application of TiN/TiO₂ composite coating in the field of friction and wear.